Beyond the boundaries of established science an avalanche of exotic ideas compete for our attention. Experts tell us that these ideas should not be permitted to take up the time of working scientists, and for the most part they are surely correct. But what about the gems in the rubble pile? By what ground-rules might we bring extraordinary new possibilities to light?

EU theory upsets lots of people. Expanding earth and earth crust displacement also illicit strong feelings. The problem with the very existence of the dinosaurs, some with their long necks and the structural problems that entails given today's gravity adds another layer of doubt about what consensus science has to offer.

The iridium layer is a fact. It was supposedly deposited as the result of one event, and consequently defines the surface of the earth at that time. It has occurred to me to ask where did all the material above that layer come from? I specifically asked that of an AskAGeologist web site and never got a straight answer in multiple emails.

Energy and matter are theoretically interchangeable. EU theory has energy entering earth continuously via the poles and I'm wondering if that energy isn't responsible for creating the matter that is expanding the earth imperceptibly on the human time scale. Could new matter be expanding the earth and consequently could rewinding the clock logically deduce a smaller earth where gravity was a fraction of today's value to allow the dinosaurs size to be reasonable under their gravity conditions? Could a slowly accreting earth cause an instability that would be rectified by earth crust displacement that would sling the mass towards the equator and help explain ancient flash frozen beasts with warm weather plant material in their stomachs?

'energy that is entering earth continuously via the poles is responsible for creating the matter that is expanding the earth imperceptibly on the human time scale'. Could new matter be expanding the earth? I believe that this could very well be a logical answer. What is flying around in space is the veryfoundation of everything that is.

perpetual motion wrote:'energy that is entering earth continuously via the poles is responsible for creating the matter that is expanding the earth imperceptibly on the human time scale'. Could new matter be expanding the earth? I believe that this could very well be a logical answer. What is flying around in space is the veryfoundation of everything that is.

That sounds similar to a Halton Arp's article discussing a variable mass hypothesis found here;

As long ago as as 1958 S. Carey reported detailed geological data which implied the earth had been expanding. K.M. Creer (1965) was one of many who showed how accurately the continents fitted together in the past and M. Kokus (1994) calculated how the observed sea floor spreading in the mid Atlantic ridge supported this interpretation. Naturally without an identifiable physical cause most scientists abandoned these empirical conclusions in favor of the theory that there was nothing of significance to explain. It is appropriate to quote Creer, however: For an adequate explanation we may well have to await a satisfactory theory of the origin and development of the universe. The variable mass theory is a candidate to fulfill that prophecy.

But how does Le Sage gravity enter this picture? I would suggest the following trial hypothesis: If much faster than light gravitions are pushing massive bodies toward each other, then they must be transmitting an impulse which could be described as energy. Is it possible that these gravitons are depositing energy or creating mass in the interior of the earth which is causing it to expand?

There are two attractive features of this suggestion. In the Olympia Meeting (1993) there were calculations that the mass of the earth had to be increasing. The problem was, however, that the mass had to be increasing too fast: To quote J.K. Davidson (Olympia Meeting p 299). The current expansion rate is very rapid and gives rise to questions like, how is the extra mass being created (it seems to be occurring in the core as there is no evidence at the surface); will the earth ultimately explode and form another asteroid belt or will it become a Jupiter then a sun... At that meeting I reminded the Geophysics section of the fact that the extragalactic quantization evidence showed that as matter evolved it must jump rapidly from one quantized particle mass value to the next highest. The obvious implication that this would be a natural explanation for the varying rate of expansion of the earth.

The second attractive feature of the variable mass theory is that the research of Tom Van Flandern (1993) indicates that planets explode. It has always been clear that where a giant planet should exist between Mars and Jupiter there is instead belt of rock fragments called the asteroids. But Van Flandern's careful work on the problem of Mars (which should in all continuity be much larger rather than much smaller than the earth) shows that it has suffered a fragmenting explosion leaving visible effects on one face. So there is evidence that this happens in the solar system. In fact there is visible evidence that it happens in galaxies as well (Arp 1998;1999).

For many years I never questioned the obvious fact that masses attracted each other (inversely as the square of their separation - to complete the mantra). The attraction was so blatant that it required no thought. But then observations of galaxies and quasars forced me to accept the fact that extragalactic redshifts were primarily intrinsic and not the result of recessional velocity in an expanding universe.

How did this lead to my abandoning pulling gravity and investigating pushing gravity? It is interesting how the crumbling of one fundamental assumption can have reverberations throughout the whole underpinning of science. In this case it was the necessity to find a mechanism which would explain intrinsic redshifts that eventually turned out to shake other fundamental assumptions. The search was motivated by a desire to have the discordant observations believed. (Unfortunately, when I asked Feynman about the Hoyle-Narlikar variable mass theory, he told me, We do not need a new theory because our present one explains everything.) Nevertheless the ball had started rolling down hill so to speak and in 1991, with Narlikar's help, I outlined in Apeiron the way in which particle masses growing with time would account for the array of accumulated extragalactic paradoxes. Later Narlikar and Arp (1993) published in the Astrophysical Journal Narlikar's original, 1977 solution of the basic dynamical equations along with the Apeiron applications to the quasar/galaxy observations.

We hoped, of course, to gain validation of the new theory by showing that it was a legitimate product of the accepted, one might even say worshipped, general relativistic field equations. All we gained in fact was an audience which totally ignored this new, more rigorous solution. Nevertheless, seeing it in print started the wheels slowly turning in my head.

The first insight came when I realized that the Friedmann solution of 1922 was based on the assumption that the masses of elementary particles were always and forever constant, m = const. He had made an approximation in a differential equation and then solved it. This is an error in mathematical procedure. What Narlikar had done was solve the equations for m = f(x,t). This a more general solution, what Tom Phipps calls a covering theory. Then if it is decided from observations that m can be set constant (e.g. locally) the solution can be used for this special case. What the Friedmann, and following Big Bang evangelists did, was succumb to the typical conceit of humans that the whole of the universe was just like themselves.

But Narlikar had overwhelmed me with the beauty of the variable mass solution by showing how the local dynamics could be recovered by the simple conformal transformation from t time (universal) to what we called τ time (our galaxy) time. The advertisement here was that our solution inherited all the physics triumphs much heralded in general relativity but also accounted for the non-local phenomena like quasar and extragalactic redshifts. Of course, to date, that still has made no impression on academic science.

In addition, I eventually realized that an important part of the variable mass solution was that it took place in perfectly at, Euclidean space. This pointed directly at the revelation that the Riemannian, geometric terms on the left hand side of the famous Gμν = Tμν equation were zero. If Gμν = 0 then the curved space-time had nothing to do with real cosmic physics.

Two thoughts then presented themselves:

1) The Gμν terms in the conventional solution usually represent forbiddingly complicated terms. But their existence appears to be required only for the purpose of compensating for the variable m in the Tμν side of the equation which was assumed constant in the Big Bang solution. These geometric terms as is well known are used to adjust parameters such as H0, q0, etc. when the redshift - apparent magnitude relation is interpreted in an expanding universe. (In the variable mass solution H0 equals only the inverse age of our galaxy and is equal to around 50 km/sec/Mpc, with no adjustable parameters.)

2) If there are no geometric space curvature terms in the variable mass solution, and this is a more valid solution, is there ever a legitimate use for these terms? For some time I entertained the idea that near high mass concentrations one might need them. But now I see work by Montanus and Gill which indicates physics with proper time and local time can reproduce classical relativity tests in at, Euclidean space. It raises the question is space-time curvature valid? At this point the elementary question that should have been asked long ago by scientists and non-scientists alike is: With any reasonable definition of space, how can one curve it? (If you have trouble visualizing curved space, try curved time!) Curved space-time appears to be, and always to have been, as Tom Phipps casually remarked, an oxymoron!

In Table 1 appended here is a summary of how conventional relativity fails and how the at space time, local and cosmic time treatments gives common sense results in its place.

Gravity

After this long preamble we finally come to the point: If space is not curved by the presence of mass (as per Einstein) - then what causes gravity? We are forced by the solution which explains the redshift dependence on age of matter to look for another cause of gravity. If masses do not move on prefixed tracks in space then there is no hope of having the instantaneously acting component of gravity by guiding them with the exchange of some electromagnetic wave travelling with c.

Since the time of the 18th century Genevan physicist, Le Sage, many people have considered what is apparently the only alternative to pulling gravity, i.e. pushing gravity. My attention, however, was belatedly called to it by articles in Tom Van Flandern's Meta Research bulletin. The key point for me was that its force behaved inversely as the square of the separation a point which I had not bothered to work out. The force (be with you) is transmitted by a surrounding sea of much faster than light gravitons. Van Flandern (1998) calculates > 2x1010c. So we can have as nearly instantaneous action as we wish and yet not abandon the concept of causality.

Of course it interesting to comment on some of the doctrinal problems of the imminently deceased relativity theory. Are inertial and gravitational mass the same? Since the atoms of a feather and of a lead ball are made of the same electrons, protons and neutrons, we will have, to some orders anyway, the same force applied by the absorption from the surrounding sea of gravitons. So the equivalence principle holds. But only if the absorption of gravitons, and subsequent impetus, is proportional to inertial mass.

My own working hypothesis for gravity is now that gravitons are very low mass particles with a huge De Broglie wavelength compared to photons. Since their wavelength is so long they have much less interaction with the intergalactic medium. So they far exceed the normal velocity of light in vacuum (i.e. the vacuum that light in our locality of the universe sees). In other words the photon is transmitted through the average cosmic false vacuum, material vacuum or zero point energy field - to use just a few names given to the old fashioned concept of aether. But the graviton interacts with much less of this molasses and hence moves much faster. One might speculate that there is a vast amount of matter in the universe which radiates at very long wavelengths.

Perhaps it is time to wander back to the observations with our new hypothesis in hand. Since the particles of matter in the universe grow as they age and communicate with ever more distant parts of the universe they have to receive information. In the variable mass theory this electromagnetic communication is at the speed of light, c. The gravitons travelling much faster than the speed of light, however, must also carry information. (No one could argue that knowledge of the direction of an adjoining mass is not information). So the old relativistic shibboleth information cannot be transmitted faster than the speed of light falls by the wayside. Recent experiments with entangled quantum states may also be indicating this.

As the inertial mass of particulate matter grows with time, in order to conserve momentum it must slow its velocity with respect to the primary reference frame. This is an important contribution of the new physics because the observations show that newly created, high redshift quasars are initially ejected as a near zero mass plasma with very high velocities and then grow in mass, drop in redshift and slow in velocity until they eventually form groups of slightly younger companions to the parent galaxy. This is observationally established and can only be explained by the variable mass theory.

The condensation of low mass plasma into a coherent body in the new theory forms an interesting contrast to condensation of galaxies in the 78 year old Big Bang theory. Bernard Bligh (2000) has shown thermodynamically that the hot Big Bang can not cool and condense into galaxies because its expansion is not constrained. As experience would dictate, a hot gas just diffuses. The situation with the near zero mass plasma is different however in that the growing mass of its constituent particles slows their velocities thereby cooling their temperature. In addition the growing mass increases the pressure toward condensing into a gravitationally bound body.

Now that we reference the primary reference frame we are reminded that this is yet another strike against the hallowed relativity theory which is supposed to have no primary reference frame. But the existence of the microwave background certainly reminds us that an average over the detectable universe certainly represents an obvious, primary reference frame. Moreover laboratory experiments like the Sagnac effect by Selleri and others reveals the presence of such a frame.

The objection by Feynman to pushing gravity which was brought to my attention by John Kierein was that objects in orbital motion such as the earth would experience resistance from increased graviton flux in the direction of their motion. The answer, without computation, seems to be that this effect would only come into action at very high orbital speeds because of the very high speed of the gravitons. But in general it should be noted that my observational experience sheds doubt on any extragalactic velocities greater than about 300 km/sec. (rotational velocities in galaxies). This would imply that older objects must come very close to rest with respect to - what else but a primary, or universal reference frame.

Quantization

An unexpected property of astronomical objects (and therefore an ignored and suppressed subject) is that their properties are quantized. This first appeared when William Tifft, showed that the redshifts of galaxies occurred in certain preferred values, e.g 72, 144, 216, etc km/sec. Later William Napier demonstrated a periodicity of 37.5 km/sec with great accuracy. The outstandingly important, empirical implication to draw from these, by now exceedingly well established observations, is that the individual velocities of galaxies must be less than about 20 km/sec otherwise the sharp quantizations would be blurred. In turn this implied very little motion in a primary reference frame.

For the quasars, Geoffrey Burbidge noticed soon after the first redshifts began to accumulate that there was a preferred value about redshift z = 1.95. As more redshifts accumulated it became clear that that the whole range of extragalactic redshifts was significantly periodic. K.G. Karlsson showed that they fit the formula (1 + zn) = (1+z0) x 1:23n.

This was interpreted by Arp in terms of variable mass theory by hypothesizing that as the electron masses grew with time that they increased through permitted mass states which stepped by a factor of 1.23.

The most astonishing result was then pointed to by Jess Artem, that the same quantization ratio that appeared in quasar redshifts appeared in the orbital parameters of the planets in the solar system. This first manifested itself in the ratio of planetary semi-major axes occurring in some high power of n in 1.23n. This also appeared to be true of the ratio of planetary and lunar masses and even solar and electron masses.

Shortly afterward O. Neto, Agnese and Festa, L. Nottale and A. and J. Rubcic independently in Brazil, Italy, France and Croatia began pointing out similarities to the Bohr atom in the orbital placement of the planets. Different variations of the Bohr-like radius = n2or n2 + 1 / 2n fit the planetary semimajor axes extremely well with rather low quantum numbers n. Most recently I have learned of a modification to the Titius-Bode law by Walter Murch where the planetary radii = 1+ 2n + 2n-1

This latter law fits the observed planetary positions exceedingly well for n = -1 to 6 with an average deviation of only 2.4 percent.

Which of these empirical laws is correct, or whether they are all different approximations to a more fundamental law is a mystery at this moment. But it is clear that the properties of the planets are not random and that they are in some way connected to quantum mechanical parameters both of which are connected to cosmological properties.

Just to try to tie some of the above results together in what is obviously an inadequate theory, let us suppose that the planetary system started as some kind of analogue to an atom. In the variable mass theory the matter starts out from zero mass but the basic unit of charge never changes. Therefore the seed planets would be placed according to Bohr atom rules. As time goes on their inertial masses grow but in steps which are governed by communication with their cosmic environment. Very soon the charge aspect of the planet is overwhelmed by its inertial mass aspect and it is thereafter governed by the currently observed gravitational laws.

Expanding Earth

As long ago as as 1958 S. Carey reported detailed geological data which implied the earth had been expanding. K.M. Creer (1965) was one of many who showed how accurately the continents fitted together in the past and M. Kokus (1994) calculated how the observed sea floor spreading in the mid Atlantic ridge supported this interpretation. Naturally without an identifiable physical cause most scientists abandoned these empirical conclusions in favor of the theory that there was nothing of significance to explain. It is appropriate to quote Creer, however: For an adequate explanation we may well have to await a satisfactory theory of the origin and development of the universe. The variable mass theory is a candidate to fulfill that prophecy.

But how does Le Sage gravity enter this picture? I would suggest the following trial hypothesis: If much faster than light gravitions are pushing massive bodies toward each other, then they must be transmitting an impulse which could be described as energy. Is it possible that these gravitons are depositing energy or creating mass in the interior of the earth which is causing it to expand?

There are two attractive features of this suggestion. In the Olympia Meeting (1993) there were calculations that the mass of the earth had to be increasing. The problem was, however, that the mass had to be increasing too fast: To quote J.K. Davidson (Olympia Meeting p 299). The current expansion rate is very rapid and gives rise to questions like, how is the extra mass being created (it seems to be occurring in the core as there is no evidence at the surface); will the earth ultimately explode and form another asteroid belt or will it become a Jupiter then a sun... At that meeting I reminded the Geophysics section of the fact that the extragalactic quantization evidence showed that as matter evolved it must jump rapidly from one quantized particle mass value to the next highest. The obvious implication that this would be a natural explanation for the varying rate of expansion of the earth.

The second attractive feature of the variable mass theory is that the research of Tom Van Flandern (1993) indicates that planets explode. It has always been clear that where a giant planet should exist between Mars and Jupiter there is instead belt of rock fragments called the asteroids. But Van Flandern's careful work on the problem of Mars (which should in all continuity be much larger rather than much smaller than the earth) shows that it has suffered a fragmenting explosion leaving visible effects on one face. So there is evidence that this happens in the solar system. In fact there is visible evidence that it happens in galaxies as well (Arp 1998;1999).

The Current State

The most intriguing problem to me now is to combine the features of the the variable mass solution with the features of the pushing gravity models. The Machian communication of the variable mass solution with matter at increasing distances offers a solution for the quantization values as reflecting discrete drops in mean density as we proceed outward in a hierarchical universe (Narlikar and Arp 2000). But that communication is electromagnetic at the velocity of light. Is it possible to transfer the periodically increasing mass with photons that resonate with the frequency of the electrons and protons in the matter under consideration? Or does this resonance frequency of the electron for example (Milo Wolff 1995) just make it possible for the much smaller, much faster than light gravitons to deposit new mass in older material.

As important as the details are, the observations overall seem now to generally require new matter to continually materialize at various points in the universe. Balance, if necessary, could be obtained from feedback mechanisms between the intergalactic aether and long wavelength radiation from present matter (I presume). The greatest part of the progress independent researchers have made in the past decades, in my opinion, is to break free of the observationally disproved dogma of curved space time, dark matter, Big Bang, no primary reference frame and no faster than light information.

Researchers found rocks in the area 412km west of Cairns were unlike any others in Australia, but similar to those in Canada

Naaman ZhouLast modified on Fri 19 Jan 2018 06.16 EST The Georgetown terrane of present-day northern Queensland was originally part of North America some 1,7bn years ago.

Geologists in northern Australia have made a discovery that suggests the area around Georgetown in northern Queensland was once part of North America, more than a billion years ago.

Researchers from Curtin University discovered that rocks in the area, 412km west of Cairns, were unlike any other rock deposits in Australia, but similar to those found in Canada.

This means that the Georgetown area – with a current population of roughly 250 – was originally a part of North America, and only collided with the rest of the Australian land mass during the formation of the ancient supercontinent Nuna (also known as Columbia) 1.7bn years ago.

A graphic showing how part of Queensland was attached to North America as part of the supercontinent Nuna.

A graphic showing how part of Queensland was attached to North America as part of the supercontinent Nuna. Photograph: Curtin UniversityNuna predates the supercontinent Pangea by 1.3bn years, and was formed as part of what geologists describe as the supercontinent cycle – where tectonic movements over Earth’s history have repeatedly created and destroyed supercontinents.

Pangea, a relatively recent supercontinent, is believed to have formed 335m years ago and began breaking apart 175m years ago. Nuna is believed to have formed 1.7bn years ago, and to have broken apart after 100m years.

Based on the Georgetown discovery, researchers now believe that the whole of northern Queensland was a part of North America that collided with Australia when Nuna formed. When the supercontinent drifted apart, it broke off and stuck to Australia.

The lead researcher, Adam Nordsvan, said the Georgetown area likely collided with the Mount Isa region of Queensland.

Rock near Georgetown was found to be not like any other rock in Australia but closely related to rock in North America.

Rock near Georgetown was found to be not like any other rock in Australia but closely related to rock in North America. Photograph: Curtin University“We found that in Mount Isa the rocks were very typically Australian,” he told Guardian Australia. “We can tie them to other parts of Australia. Surprisingly, in Georgetown – about 500km away – we found signatures that were completely unknown to the Australian continent, and are remarkably similar to North America.”

He said preliminary data suggested the whole of northern Queensland above Georgetown could have been part of North America at the time.

“We are expecting more data this year that will definitely show whether or not they are the same, but it is likely that the whole northern tip of Queensland is North American. That’s one of the implications of the paper.”

He said that links between Australia and North America had first been proposed in the late 1970s, and further researched in the early 1990s. In models of other supercontinents, such as Rodinia (formed after the breakup of Nuna), eastern Australia has been connected by geologists to the west of North America.

“On the North American side, some great research has come out showing the connection was likely at that time [of Nuna],” Nordsvan said. “In Australia there has been a little bit of research that shows the connection was likely there. This is probably the first piece of really good evidence that at 1.7bn or 1.6bn years ago, there was definitely a connection between the two continents.”

The paper was co-authored by researchers from Monash University and the Geological Survey of Queensland, and was published in the journal Geology.

This shows how the Earth fits together. Notice Australia nestles up against North America.

This month's edition of the AAPG (American Association of Petroleum Geologists) magazine, 'Explorer', has a discussion by geologist Keith James about the various anomalies and shortcomings that dog the plate tectonics model.

A couple of the talking points, first, metamorphics that don't appear to have been buried.

... Blueschists (high-pressure/low-temperature metamorphism) are seen as classic indicators of fossil subduction zones, involving descent of material to 40–80 kilometers over millions of years, metamorphism, and then unexplained resurrection. However, some radiometric data suggest metamorphism only slightly younger than predecessor rocks. There are no blueschists in the Central American or Lesser Antilles subduction arcs. Along the north and south Caribbean margins, metamorphism increases and high-pressure/low-temperature rocks occur close to strike-slip faults [mainly horizontal displacement]. Some are even interbedded with sedimentary equivalents.

Next, some numerical curiousities

... The reconstructions use constant size Earth. There are 75,000 kilometers of “spreading” ridges and only 30,500 kilometers of trenches and 9,000 kilometers of collision zones. Production of more crust than consumption implies that the Earth is expanding. Space-geodetic data show that the solid Earth expanded about 0.24 millimeters annually in recent decades. Growth increments on fossil corals and brachiopods show that days per year declined from 424 in the Middle Cambrian to 365 today – like a pirouetting ballerina extending her arms, Earth grows and slows. How?

He suggests that volume increase via serpentinization (where the orginal rock interacts with water which changes the rock's crystal structure and volume) may produce radial growth.

... Serpentinization of shallow mantle peridotite results in up to 40-percent volume increase and release of heat. Is this responsible for elevation of MORs, with their black smokers? Does radial growth contribute to continental separation, extension and subsidence?

And lastly, his prognosis for Plate Tectonics,

... Meanwhile, published PT teaching is complacent. It should adapt to emerging data, include multiple working hypotheses and enable students to think and choose. If not, the writing in stone might eventually read “RIP.”

That is a fun article, starting on page 18, "Not Written in Stone". I need to read it again, figuring out the geological definitions that they use.

It's fun, like you say, that he uses expansion based on "(where the original rock interacts with water which changes the rock's crystal structure and volume)". Yet we have shown that gravity has increased over time from adding new material to the Earth.

What I have fun with is he is expecting criticism from the conservatives because he is pointing out "subsided continents" that used to connect the continents -- that you should drill for oil there. HA!

moonkoon wrote:... Serpentinization of shallow mantle peridotite results in up to 40-percent volume increase and release of heat. Is this responsible for elevation of MORs, with their black smokers? Does radial growth contribute to continental separation, extension and subsidence?

Serpentinization is a source of hydrogen which in turn can reduce any carbonate or carbon dioxide in the vicinity to methane (the reduced carbon combines with the hydrogen). Mantle type rocks such as basalt often play host to inclusions or veins of calcite (a carbonate).

... Serpentinization of ultramafic rocks occurring in mid-ocean ridges, forearc systems, and terrestrial ophiolites (i.e., obducted/accretionary oceanic crust) on Earth is a geochemical and water-dependent process that results in a variety of gas and fluid species. Molecular hydrogen (H2) is the most influential and relevant species in the abiotic synthesis of organic compounds produced as a consequence of serpentinization due to its ability to reduce carbon (... carbonate etc.) and produce methane (CH4) and a wide variety of other organic compounds.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4523005/

This says nothing about the ultimate source of the hydrogen (or the water for that matter) so it can't be taken as a falsification of a hydritic core model.

On a more general note, limited radial expansion via serpentinization might provide a temporary lifeline for P/T but it does not account for the current size of ocean basins which require four or five fold expansion.

Approx 93% of mantle volume is thought to be oxygen. This is the obvious prime candidate for volume increase.

I speculate that the mechanism may be some type of as yet unidentified nuclear conversion process (not the well documented fission process) where iron or silicon transmutes into (mainly) oxygen. It could also imply that our concept of energy may be incomplete.

For me the most interesting bit was the thinning and extension of the crust. At the moment i'm thinking we shifted to a more distant orbit which implies a massive sudden drop in the planets velocity and the consequent heating from the conversion of kinetic energy. I'm only a quarter of the way through the topic though.

James Maxlow continued Carey's work. This lecture lays out everything up to now. He talks about the fossil record and the geological record. I hate to says this, but what he did is "Science" not opinion, so be sure to watch the complete lecture multiple times.

A new study argues humans caused a rainforest crisis, but not everyone's convinced.

Kiona N. Smith - 2/27/2018, 4:35 PM

EnlargePNASThree thousand years ago, dense old-growth rainforests covered most of central Africa. But around 2,600 years ago, an event that ecologists call the Late Holocene Rainforest Crisis occurred, and the forests suddenly gave way to savannas dotted with islands of trees. Six hundred years later, the forests grew back almost as swiftly as they had vanished.

But for the last 20 years, paleoecologists have debated what caused the Rainforest Crisis. Most thought that the region’s climate changed, bringing either less annual rain or a longer dry season with a short but intense monsoon. That climate shift, many paleoecologists argue, devastated the rainforests of central Africa but created perfect conditions for savannas. But a new study proposes that humans may actually have been the culprits.

A question of timing

Around the time of the Rainforest Crisis, farmers from northern Africa started migrating southward, bringing with them an advanced culture of pearl-millet cultivation, ironworking, and palm-oil harvesting, all of which take a toll on the landscape. Those northern farmers spoke Bantu languages, which are still spoken by about 300 million people in Africa today.

The currently accepted version among paleoecologists is that warming sea-surface temperatures in the Gulf of Guinea caused a shift in the region’s monsoon cycle, leading to a longer, drier dry season, so people migrated south to farm millet on the open grasslands. But University of Potsdam paleoecologist Yannick Garcin and his colleagues, who just published a new study on the Rainforest Crisis, argue that it happened the other way around: people moved south into the rainforest and cleared land to plant millet. And when their population crashed 600 years later, the rainforest rebounded.

Most of the debate hinges on whether those millet farmers moved south during the Rainforest Crisis or before and on whether there’s evidence of climate shift at the same time. And among paleoecologists and archaeologists, the debate is heating up. If you’re not a paleoecologist, the whole debate may seem a little esoteric, but it’s a great example of the scientific process at work, with both sides presenting their own sets of evidence and debating which is most accurate and whose interpretation best fits the data.

Dueling data

Paleoarchaeologist Jean Maley and his colleagues published a paper in October 2017 in which they argued for the climate hypothesis, citing sediment layers found in lakes in Ghana, Gabon, and the Congo. These show evidence of increased erosion around 2,650 years ago—presumably thanks to more intense monsoon rains. That lines up well with the other evidence for the climate shift.

And an earlier study sampled pollen from the sediments at the bottom of Lake Victoria, which showed that the water level 2,200 years ago was much lower than it is today and that savanna had taken over land formerly shaded by rainforest canopies.

On the other hand, Garcin and his colleagues recently took a sediment core from Lake Barombi in Cameroon. The 12-meter-long cylinder of mud held 10,500 years’ worth of accumulated sediment layers, which contained microscopic bits of material called plant waxes. Plants secrete waxy mixtures of lipids to protect their outer cells, and these waxes can last for thousands of years in soil. Conveniently for paleoecologists, they record what ratio of hydrogen isotopes the plant got from its water, as well as how the plant handled carbon.

Coring platform on Lake BarombiEnlarge / Coring platform on Lake BarombiPNASWoody plants like trees and shrubs obtain carbon differently from grasses, so their plant waxes end up with different ratios of the stable isotope carbon-13. Prior to 2,600 years ago, the plant waxes in Lake Barombi seemed to be from mostly trees and shrubs, exactly what you’d expect in a thriving rainforest. But within a century, carbon-13 ratios in the plant waxes washing into Lake Barombi started looking much more like grassland than forest, which matched the pollen data from other studies. After about 600 years, though, the carbon-14 signature of forests replaced the grasslands.

Crisis or cause?

Those findings more or less confirmed what the pollen studies had to say about the timing of the Rainforest Crisis, but it didn’t say anything about what caused the event. But the ratio of hydrogen isotopes in plant waxes can reveal information about climate because, on a scale of decades, those ratios generally line up with average annual rainfall. In the Lake Barombi sediment core, that evidence pointed to a long, gradual drying tend from 7,000 to 2,000 years ago, but there didn’t seem to be any sudden climate shift near the beginning of the Rainforest Crisis. In fact, according to the Lake Barombi data, the area was actually wetter during the Rainforest Crisis than it is now, and today it’s still mostly covered with rainforest.

Tiny shells preserved in sediment cores from the Gulf of Guinea didn’t contain any evidence of a change in sea surface temperature, according to Garcin and his colleagues.

But when they examined a database of 460 archaeological sites from around the region, they found that very few sites had been dated to earlier than 4000 years ago. Human activity seems to have started picking up in the region around then, and it really exploded around 2,600 years ago. Garcin and his colleagues say that’s evidence of a major population increase right around the beginning of the Rainforest Crisis.

They claim this study is clear evidence that people, not climate, caused the Late Holocene Rainforest Crisis. But not everyone is convinced. Maley told Ars Technica that the most important argument against the blame-the-humans hypothesis and in favor of a shift in climate is the sheer geographic scale of the Rainforest Crisis—it happened at nearly the same time from the Equator to the southern Sahara. Humans, on the other hand, didn’t migrate south into central Africa’s rainforests with same kind of synchronization.

In other words, the debate over what happened to central Africa’s Late Holocene rainforests is far from settled.

Lake BarombiPNASScience in progress

Paleoecologists, archaeologists, and even linguists are still weighing in with new lines of evidence, and it’s likely to be some time before they reach a consensus. Part of the uncertainty is due to the limited resolution of dating methods, whether it’s radiocarbon dating or counting layers in a sediment core.

For instance, some of the evidence for the climate hypothesis comes from pollen and diatoms from the bottom of nearby Lake Ossa. But Garcin and his colleagues claim that, due to aged carbon in the sediment itself, there’s about a 400-year uncertainty in dating those layers. And in Garcin’s data, the Rainforest Crisis appears to have started at Lake Barombi about 200 years before Bantu agricultural sites started turning up in the region.

“We answer that we are at the limit of the precision of the dating method used to resolve such a small lag,” said Garcin, “and since the Lake Barombi is at the northern edge of Central Africa, it may have witnessed first those human impacts compared to the rest of the whole region.”

One thing scientists on all sides agree on is that it’s important to understand the cause of past events like this, because reconstructing past climate events can help predict how humans, climate, and vulnerable ecosystems might interact in the future. And in some ways, the Rainforest Crisis is an encouraging story, because it means the rainforest can bounce back from deforestation.

“Rainforest ecosystems are very sensitive to disturbances but also resilient,” said Garcin.